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From "Dan Hecht (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5713: always reserve memory for preaggs
Date Wed, 23 Aug 2017 20:47:28 GMT
Dan Hecht has posted comments on this change.

Change subject: IMPALA-5713: always reserve memory for preaggs
......................................................................


Patch Set 3:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/7739/3/fe/src/main/java/org/apache/impala/planner/AggregationNode.java
File fe/src/main/java/org/apache/impala/planner/AggregationNode.java:

PS3, Line 327: 16b
should we add a static_assert to backend to update this if needed, or you think it doesn't
matter enough?


Line 330:         perInstanceMinReservation = (bufferSize + 64 * 1024) * PARTITION_FANOUT;
this means we end up reserving around the same amount of memory for streaming pre-agg, right?
 wasn't one of the points of streaming pre-agg to help when under memory pressure?  should
we set a smaller bufferSize for streaming preagg? since they won't spill anyway, the buffer
size shouldn't matter that much for perf, right?  hmm, except for TLB, I guess.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I2b544f9ec1a906719e2bbb074743926b95a3a573
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dhecht@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-HasComments: Yes

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